Semi-conductor trigger circuit



A ril 16, 1957. M, L wcpp Re. 24,303

' v saux-connuc'roa TRIGGER CIRCUIT Original Filed July 2, 1951 r 4Sheets-Sheet l FIGJ. F|G.2.

CURRENT m MAI l23456789 l0'i|l2l3- \NVENTOR e m VOLTS MARION 1.. W000'BY I ATTORNEY April 16, 1957 v W Re. 24,303

SEMI-CONDUCTOR TRIGGER CIRCUIT .Original Filed July 2. 1951 4Sheets-Sheet 3 g IN VOLTS FlG.2d.

0 IO p o 'vw mmauuna mvzmoh MARION L. wooo ATTORNEY United StatesPatent:

1. 24,3113 SEMLCONDUCTOR TRIGGER, CIRCUIT MiirlonLoren Wood; UlsterCounty, N. Y., assignor to International Business Machines Corporation,New York, N. Y., a corporation of New York o i' a 1v..2, 6s1 ,72s, datedSeptember s, 1953, set-n1 0. "234,837; any 2, 1951'; Application forreissue Alignstlp,"1955,.SerialNo. 529,502. reclaims. c1.- save-88.5.

Matterjenclosed'in heavy. brackets appears in the orlglnialpatentbutffbrm's nop'art of this reissue specificafionr'matter printed in italicsindicates the" additions mi'cle by reissue;

This inventionrelates inigenerat to a trigger circuit and inparticularto a bi-stable trigger circuit arrangement employing 'a' pairofsemi-eonduetive elements.

The principal obj-ectof the invent-ion is. to provide a trigger circuitincluding a pair: of semi-conducting elements and having twoz-stablest'atesof. equilibrium.

Another object ofth'e invention is' to provide a bistableqxtriggercircuit including. a pair of variable impedancezelements each of which.is. characterized by a regiomofi positivevariational resistanceaand aregion of negative variational resistance.

A further object of the'invention is to provide a bistable triggercircuit includinga: pair of semi-conducting elementscinwhichthetriggeringaction does not depend upon.- aregenerative or positivefeedback circuit connection:

A still further object of the invention is to provide a bi-stabletrig'ger circuit includingi a pair of semi-conductorseach of which ischaracteri'zed -by the current flowing therethl'oughbeing-- a 'bi-valuedfunction of the voltage.

ether objects ofthe: invention will be pointed out in the: followingdescription andclaims and illustrated in "rig drawings, which disclose,by way of examples, th principle of the invention and the best mode,whichhas'been contemplated, of applying that principle.

In the drawings:

Fig. 1 is a's'eries circuit including a crystal diode, a resi-storEand-asource of potential;

Fig-. Z is a circuit diagram representative of the main embodimentof theinvention;

' Figs: 2a, 2b, 2c and Zd'are a-series of characteristic curves'rep'resenting' the operatingconditions of the circuit ar angement orFigi2-;

Big". 3 i's'a'modific'ation of-Fig. 2in which a three elect'rodesemhconductorelement is used inplace of a crystal diodeg i Fig; his aseries'of characteristic curve-s representing the operating conditionsofFig. 3;

Fi'gs'z' 4 and 5' are modificationso'f the circuit arrangement ofFig3;'and

Fig. isa binary counter arrangement incorporating the present invention.

crystn diode includes a minute block of doped semiconductor which ischaracterized by a region of positive variational resistanceand a regionof negative variational resistance such as, for example, germanium orsilicon; The semi-conductor block is plated with rnetal on one surfaceand connected with an extremely fine metallic whisker on the parallelsurface. The positive resistance characteristic of the diode may bedefined as one; in" Which there i s'a change in current in the samesense to; each change of potential, while in the case of the negativeresistance characteristic the current varies inversely withthewoltagcrNow; referring in-detail to Fig. 1-, there. is shown. therein a sourceof operating potential 12 of the'magnitude of approximately 315 volts, a0.92 megohrn resistorv 11 and a crystal diode 10, all connected inseries. The crystal diode 10 includes a-bloclt of semi-conductormaterial 17 which isplated with a metallic base 13 on one surface andconnected with an extremely fine metallic whisker 14 on a parallelsurface. The intersection of the-load line 13 and the crystal diodecharacteristic'curve 9 at point 20-, as'shown in the diagram ofFig; 2a,determine the operating point for this series circuit arrangementwherethe values of the source of potential 12 and the resistor 1 are soselected such that theload line 18 willintersect curve 9 in its regionof negative variational resistance;

it the input characteristic of this series'circuit arrange: ment isdetermined across the terminals 15 and 16 (Fig. 1) it will be found tobe thatas shown 'by the curve 21 (Fig. 2b). It now becomes apparent thatthis input characteristic curve 21 serves in reality as a. load linefor'any device that may be connected in parallelwith the diode 10. Withregard to the input characteristic curve 21, it has been determinedexperimentally that the diode'lt) is in a region ofpositive variationalresistance for the portion 21b to 210 of the curve 21 andiin a region ofnegative variational resistance for the portion 21b to 21a of the curve21. Now if a second crystal diode 22 is connected in parallel with thediode 19, such as shown in Pig. 2, it will be seen that the inputcharacteristic curve 21 intersects the curve 55 representative of thecharacteristic of the crystal diode 22 at the stable points of operation23 and 24 (Fig. 2c). The input characteristic curve 56 (Fig. 2b)represents the characteristic obtained when one looks into a seriescircuit similar to that of Fig. 1' in which the crystal diode 22 is usedin place of the diode it). it is to be noted that if diode 22' wereidentical to diode 19, curve 56 would be identical to curve 21; however,for the sake of generality, it is assumed that the diodes are notidentical.

The circuit diagram of Fig. 2 represents the main embodiment of theinvention and functions as a trigger circuit in a manner to be presentlydescribed. When the trigger circuit is on or in one of the two stableoperating positions, the'crystal diode 10 operates at point 57 (Fig, 2d)in its region of negative resistance while the crystal diode 22 operatesat point 23 in its region of positive variational resistance. In thisoperating position it is to be noted from Fig. 2d that the diode 10 isat the higher while the diode 22 is at the lesser of two currentconditions with the voltage'drop across the two diodes being necessarilythe same, because they are connected in parallel. In the other stablestate of equilibrium, arbitrarily called the off state, crystal diode 22will operate at point 24 in its region of negative variationalresistance, while the diode 10 operates at point 58 in its region ofpositive variational resistance. In this operating position, the currentflow through the diode 22 will be at the higher of two values While thecurrent flow through the diode 10 will be at the lower of two values.Also when either of the crystal diodes is operating in its region ofnegative variational resistance, the current therethrough exceeds thatthrough the other crystal diode which is operating in its region ofpositive variational resistance.

Assuming that in one state of equilibrium one of the diodes will be in apositive resistance region While the other diode will be in a negativeresistance region, the triggering of the circuit arrangement of Fig. 2may be brought about through the manipulation of the switches 25 and 26.When the switches are operated in a manner to be presently described,the diodes will assume the operating positions of the other state ofequilibrium such that the diode. in the positive resistance region willshift to the negative resistance region while the diode in the negativeresistance region will shift to the positive resistance region. This maybe shown by referring to Fig. 2 and assuming that the switch 25 isclosed while the switch 26 is open causing diode to operate at point(Figs. 2a and 2d) in its negative resistance region. Now with the switchin a closed position, the closing of switch 26 will connect the diodes10 and 22 in parallel but since the voltage available to the diode 22 isless than the peak inverse voltage, as represented by point 27, thediode 22 will operate in a positive resistance region at position 23,and diode 10 will shift in its operating point to 57 due to the presenceof diode 22 in the circuit. Now if we open the switch 25 and leave theswitch 26 closed, the diode 22 will switch from the operating point 23located in its positive resistance region to the operating point 59 inthe negative resistance region inasmuch as the magnitudes of the battery12 and the resistor [17] 11 have been so selected as to cause the singlediode to assume this negative position. Next, if We close the switch 26with the switch 25 also in a closed position, the diode 10 will assumeoperating point 58 in the positive resistance region inasmuch as thevoltage available to the diode 10 at this time is less than the peakinverse voltage while the diode 22 will remain in the negativeresistance region but will shift to position 24.

A modification of Fig. 2 which offers a more practical arrangement forproducing a change in the statusof the trigger circuit is shown in Fig.3. In this modification each of the crystal diodes is replaced by acrystal triode or transistor, as it is more commonly known.

The crystal triode or transistor 28 (Fig. 3) includes a block ofsemi-conductive material which is plated with a metallic base 29 on onesurface and connected with a pair of extremely fine metallic electrodes30 and 31, commonly referred to as the collector and the emitter,respectively. The collector 30 is coupled to the negative side of a 67.5volt supply source 32 While the emitter is coupled to the positive sideof said source through a 13,000 ohm resistor 33. The base electrode 29is coupled through a 430 ohm resistor 34 to the junction of the emitterelectrode 31 and the resistor 33. These various connections of the threeelectrodes cause the collector 30 to be biased negatively with respectto the remaining two electrodes 29 and 31 while the emitter 31 is biasedpositively with respect to the base electrode 29. A second transistor orvariable impedance element 35 is connected in parallel with the triode28. The triode 35 has a base electrode 36, a collector electrode 37, andan emitter electrode 38 which are connected in the manner as previouslydescribed for the identical electrodes of the triode 28. The pulsegenerators 39 and 40 representative of a source of out-of-phase negativepulses are connected through the corresponding capacitors 41 and 42 tothe respective base electrodes 29 and 36 of the transistors 28 and 35.

As is well known, and as pointed out in the copending application of A.H. Dickinson, Serial No. 208,966, filed February 1, 1951, a variation inthe emitter potential produces a change in the collector characteristiccurve 43 (Fig. 3a) which curve is similar in nature to thecharacteristic curve 9 (Fig. 2a) of the crystal diode. The collectorcharacteristic curve 43 is representative of the characteristic curveobtained for the triode 35 while the curve 66 is the characteristiccurve for the triode 28. The input characteristic curves 62 and 61 wereobtained in a manner similar to that described with reference to Fig. iwhere curve 61 is the input characteristic with triode 28 in series withsource of potential 32 and resister 33, and curve 62 is the inputcharacteristic when triode 35 is similarly employed.

The method of causing a shift in the status of the trigger circuit ofFig. 3 will now be described with an 4 initial assumption being madethat the transistor 35 is operating at point 45 in the positivevariational resistance region of the curve 43 and the transistor 28 isoperating at point 46 in the negative variational resistance region of,the curve 60 (Fig. 3a). It is to be observed from Fig. 3a that at thisposition of stability the current through the transistor 35 is at thelower of two values while the current through the transistor 28 is atthe higher of two values.

Upon applying a negative pulse from the source 40 through the capacitor42 to the base electrode 36 of the transistor 35, the emitter to basepotential thereof will be increased thereby causing a shift in thecharacteristic curve 43 to the dash line curve 47 as explained in the A.H. Dickinson application Serial No. 208,966. The change in the collectorcharacteristic curve reduces the voltage at which the transistor 35 goesinto its region of negative variational resistance and as a result thetransistor 35 shifts to the operating point 48. The operating point 43of the triode 35 will shift to operating point 63 upon the cessation ofthe negative pulse applied to the base electrode. With the transistor 35operating in its region of negative resistance, the transistor 28 shiftsfrom point 46 to operating point 64 in the positive resistance region asdemanded by the stability criteria of the circuit. Thus a change instatus of the trigger circuit of Fig. 3 has occurred in which thetransistor 28 is operating at position 64 while the transistor 35 isoperating at position 63. In this new stable point of equilibrium thecurrent flow through the transistor 35 is now at the higher of twovalues 'while the current flow through the transistor 28 is now at thelower of two values.

In a similar manner, the application of a negative pulse from the source39 through the capacitor 41 to the triode 28 will switch the triggerback to the status originally assumed.

A modification of Fig. 3 is shown in Fig. 4 wherein the functions of theemitter and base, as shown in Fig. 3, are interchanged, and a pair ofresistors, 50 and 53, for purposes of deriving an output, are added. Inthis arrangement of Fig. 4, the collector electrode 30 of the transistor28 is connected to the negative side of the battery through the resistor50 while the emitter 31 is coupled to the positive side of the battery32 through a pair of resistors 34 and 33. The source of positive pulses39 is coupled through the capacitor 41 to the emitter electrode 28. Thetransistor 35 which is connected in parallel with the transistor 28 issimilarly coupled. In this modification the emitter electrode is madepositive with respect to the base electrode thereby enabling the circuitto be made responsive to positive pulses instead of negative pulses.

A further modification of Fig. 3 is that shown in Fig; 5. In thismodification the collector electrode 30 is coupled to the negativeterminal of the battery 32 through a parallel impedance networkconsisting of the 570 ohm resistor 50 and the .0056 microfarad capacitor51. In like manner the collector electrode 37 is coupled through theparallel network consisting of the 570 ohm resistor 53 and the .0056microfarad capacitor 52 to the negative side of the battery 32. A sourceof negative pulses 54 is jointly coupled through the capacitors 41 and42 to the respective base electrodes 29 and 36. The insertion of theimpedance network in each of the collector circuits in addition to thejoint coupling of the pulse source with the base electrodes of eachtransistor enables the circuit arrangement of Fig. 5 to function as awell known flipfiop circuit in which successive negative pulses appliedsimultaneously to each of the base electrodes causes the trigger toreverse back and forth in status.

For example, let it be assumed that the transistor 35 is operating atpoint 63 (Fig. 3a) in the region of negative resistance while thetransistor 28 is operating at point 64 in the region of positiveresistance when a negative pulse is simultaneously applied to thebaseelectrodes of the triodes 28 and 35. The negative pulse applied tocausingthe transistor-28 to shift to thenegative resistance regionwhich, in turn, will cause the transistor 35 to; shift to the positiveresistanceregion-thereby resulting in the trigger circuit assuming/theother state of equilibrium.

The next-following. negative pulse will cause the trigger circuitto-shift; back to its original state of equilibrium.

In Fig.6, a two stage pulse counter is formed by capacitively' couplingthe trigger circuit of Fig. 5 with a similar trigger circuit. While onlytwo stagesare shown it is pointed out-,that it iswithin the scope oftheinvention to connect two or more trigger circuits as a decade counter inamanner which is well known in the art. The output taken across-theresistors 53 of the first stage is applied jointly through the 0.05microfarad capacitor 54 to each of.the base electrodes of the secondstage such that exchange instatus of the second stageoccurs for onlyevery. second, negative pulseapplied to'th'e input side of the. first.stage.

While there have been shown and" described and pointed'outthe-fundamental novel features of the invention as applied' to apreferred embodiment, it will be understood th'at various omissions andsubstitutions and changesin the form anddetails of the deviceillustrated and in" its operation may be made by those skilled in theart,, without departingtrom the spirit of the invention. It-is theintentionj. herefore, tobe limited only as. indicat'ed'by' the scopeofthe following. claims.

What is. claimed is:

1'. A bi-stable trigger circuit comprising a plurality of variableimpedance elements, each having a current/voltage relationshipsucli thatthe current is a multi-value functionof the voltage, a source of currentand'means for initiating a change in the distribution, of the currentflow fromsaid source [of current] between said'elements, the currentthrough one ofsaid'elements in one stateof equilibrium exceeding thecurrent through the other of said elements, while the current throughsaid other of said elements in the other state of equilibrium exceedsthe current through said'one. of said elements;

2. A'trigger circuit 'having two stable operating conditions comprisingapa'ir of parallel connected variable 'impedanc'e'elements, eachincluding a semi-conductor element having different [resistance]impedance characteristics in each-of saidconditions, a: source ofcurrent, the current flow through one of said'elements being greaterthan that" through the other ofsaid elements in-one of sai'd'conditions,and viceversa,.in the. otherof said conditions, and means for initiatinga change in the distribution of the current flow from saidsource [ofcurrent] between said elements.

3. In a trigger circuit having two, stable states of equilibrium, a pairof [crystal] semi-conductor diodes, a source of potential,- impedancemeans, means-- for" sequentially'coupling firstone-of said'diodcs inseries with said source and-impedance means, then saiddiodes inparallelwitlr said source and-impedancemeans', and then the otherofsaiddiodesin'serieswith said source and saidimpedancesuchthat-'the-status of said trigger shifts from =one stiate-ofequilibrium to another.

4. A bi-stabletriggercircuit comprising a pairofvariableimpedanceelements each having a characteristic including aregion of positive and negative variational resistance, a source ofpotential and a resistor serially arranged, and means for sequentiallycoupling first one of said elements and then the other of said elementsin series with said resistor, said circuit shifting from one status tothe other as said elements are serially coupled by said sequentialmeans.

5. A trigger circuit having two stable points of equilibrium comprising[a] first and second semi-conductor devices, each having a plurality ofelectrodes, means for applying operating potentials to saidelcctrodes[,] including means for coupling said first and secondsemiconductor devices. in paraliei, a nd, rneans foralternately applying[ncgativelinpnt pulses iQ i'QIXG Ofsaid-electrodes of-said first andsecond sem conductor dev-icesforcausing a shift; in status of saidtrigger circuit.

6.- A bi-stable triggercircuit comprising [al.first and second-[crystaltriode]. transistors; each having a collector, an. emitter. and; a baseelectrode-- coupled to a semi conductive elemcnt,,- means for coupling[said first and-second triode inparallel] atleast two- 0f the electrodesof one transistor to corresponding electrodes 0f the other transistor byrespective direct' connections, means including; a common impedanceelementf.fotapplying operating potentials; to" said first and second[triode] transistors, there being no cross-connection be tween-theelectrodesofi sa-idtransistors,;.- and-pulse meanscoupledttoeachsaidbase electrode for sequentially causing a shift instatusof saidcircuit.

7-.v A trigger circuit'having, two stable-states ofequilibriurncomprising; a-pair; of semi-conducting. elements,each'having, a characteristicincluding a region of positive and-negativevariational re'sistancqeachof said elementshavingiabase electrode-anemitter electrode, and a'collector electrode,- means for-connecting saidelements in parallellj, meansla'nd. forapplyingoperating potentialsthereto including a common impedance element [for applying operatingpotentials tosaid" elements]; one of said elements being in'theregion-of negative resistance while'the otherofsaidvelernents is-instheregion'- of positive resistance when said circuit'isin-one of saidstates of equilibrium, and means for applying a negative pulse to'thebase electrode of; saidother of said'elements to cause said circuit toshift tothe other of said states of equilibrium;

8. A trigger circuithavi-ng two stablestates of equilibrium comprising.a first [crystaltriode]-.transistor including a firstcollectorelectrode,.-a first emitter electrode, a first base. electrodeand a. first semi-conducting element, [means for; disposinglsaidelectrodes [in operating relationship, with] operatively. contactingsaid element; asource, of operating'zpotntial having positive andnegative terminals, a' first impedance network including a resistor andcapacitor in-parallehmeans for coupling said collector, electrode tosaid; negative terminal through said network, a-first resistor means forcoupling a said base electrode to said emitter electrode, asecond[crystal triode]: transistor having;- a second collector electrode, asecond emitter electrode,:a secondbase .electrod'e, and a secondsemi-conducting clement,-said second electrodes operativelycontacting-said second'element, a second impedance network including aresistor and capacitor in parallel, means: for couplingasaid secondcollector electrode; to said negative" terminab through said: secondnetwork, a secondresistorme'ans' for coupling said second baseelectrodeto saidj second emitter electrode, impedance means commonly.coupling said first and second emitter electrodes tosaid positiveterminal, and a source of negative pulses: commonly coupled to saidfirst and second base. electrodes.

9. An impulse counter-circuit arrangementcomprising a first stageincludinga first triggercircuit and a second stage includingasecon'dtrigger" circuit, said first'and second circuits each comprising a pairof scmi-conducting elements, each includingabaseelectrodeg-anemitterelectrode, a collcctor electrode, and a semi-conductor'body, saidelectrodes operatively contacting the corresponding semi-conductor body,a source of potential, means for positively biasing each said emitterelectrode with respect to the corresponding base electrode, means fornegatively biasing each said collector electrode with respect to thecorresponding base electrode, resistor means for commonly coupling eachsaid emitter electrode of said first and second circuits to the positiveterminal of said source of potential, means for applying the outputsignal of said first stage to said second stage, and means for applyingnegative pulses to said first stage.

said electrode being operably coupled said semi-conductor bodies, meanstransistors, each including [a] collector, emitter,- and baseelectrodes, and a semi-conducting element, each to the associated one ofsaid elements, a source of operating potential having positive andnegative terminals, means for coupling each said collector electrode toone of said [negative] terminals, means including a resistive elementfor coupling each said emitter electrode to the corresponding baseelectrode, means commonly coupling each said base electrode to the otherof said [positive] terminals, and means including a source of pulses ofpredetermined polarity commonly coupled to said base electrodes.

11. A pulse counter circuit arrangement comprising [a] first and secondtrigger circuits, each said circuit comprising a pair of semi-conductingdevices, each including a base electrode, an emitter electrode, acollector electrode, and a semi-conductor body, each said electrodeoperatively contacting the corresponding one of for [positively] biasingeach said emitter electrode in ne polarity with respect to thecorresponding base electrode, means for [negatively] biasing each saidcollector electrode in the opposite polarity with respect to thecorresponding base electrode, means for applying the output signal ofsaid first trigger circuit to said second trigger circuit, and means forapplying pulses of a predetermined polarity to said first triggercircuit.

12. A bi-stable trigger circuit comprising first and second transistors,each having a collector, an emitter,

and a base electrode coupled to a semi-conductive element, means forcoupling at least two of the electrodes of one transistor tocorresponding electrodes of the other transistor by respective directconnections, means including a common impedance element for applyingoperating potential to the transistors, there being no crossconnectionbetween the electrodes of said transistors, and pulse means coupled toeach said emitter electrode for sequentially causing a shift in statusof said circuit.

13. A circuit comprising first and second transistors, each having acontrol electrode and an output electrode, means for coupling at l asttwo of the electrodes of one transistor to corresponding'electrodes ofthe other transistor by respective direct connections, means including acommon impedance clement connected to said output electrodes forapplying operating potentials to the transistors, there being nocross-connection between the electrodes of said transistors, and pulsemeans coupled to each said control electrode for controlling the currentflow through said common impedance element.

14. In combination, a plurality of transistors having a like electrodeof each tied together and to a common load impedance, means foroperatively biasing said transistors through said common load impedance,and pulse means coupled to each transistor to control the current flowthrough said common impedance.

15. In combination, a plurality of transistors having a like electrodeof each tied together and to a common load impedance, means foroperatively biasing said transistors through said common load impedance,and a plurality of independent signal means, each individually coupledto a respective transistor to control the current flow through saidcommon impedance.

.a respective electrode 16. A bi-stable circuit comprising a pair oftransistors, each having an emitter electrode, a base electrode, and acollector electrode, means for operatively biasing said electrodesincluding a source of potential and a resistor serially arranged andmeans connecting both said emitter electrodes together and through saidresistor to said source, said resistor being effective to limit thetotal current from said source to a value suflicient to maintain oneonly of said transistors substantially conductive, and means operablewhen either transistor is substantially conductive to reduce theimpedance of the other transistor, thereby reversing the conductingstates of said transistors.

17. A bi-stable circuit comprising a pair of transistors, each having anemitter electrode, a base electrode, and a collector electrode, meansfor operatively biasing said electrodes including a source of potentialand a resistor serially arranged and means connecting both said baseelectrodes together and through said resistor to said source, saidresistor being efiective to limit the total current from said source toa value suflicient to maintain one only of said transistorssubstantially conductive, and means Operable when either transistor issubstantially conductive to reduce the impedance of the othertransistor, ther by r versing the conducting states of said transistors.

18. A bi-stable circuit comprising two semi-conductor diodes, eachhaving two electrodes, a source of p0tential and a resistor seriallyarranged, means connecting of each of said diod s through said resistorto said source, said resistor being effective to limit the total currentfrom said source to a value sufficient to maintain only one of saiddiodes substantially conductive, and means operable when either diode issubstantially conductive to reduce the impedance of the other diode,thereby reversing the conducting states of said diodes.

19. A bi-stable circuit comprising two semi-conductive devices, eachhaving at least two electrodes, means for operatively biasing saidelectrodes including a source of potential and a resistor seriallyarranged, and means connecting a respective electrode of each of saiddevices together and through said resistor to said source, said resistorbeing eflective to limit the total current from said source to a valuesuflicient to maintain only one of said devices substantiallyconductive, and means operable when either device is substantiallyconductive to reduce the impedance of the other device, therebyreversing the conducting states of said devices.

References Cited in the file of or the original paten UNITED STATESPATENTS this patent t

